Room Treatment Progress / 4300_behind_left_speaker Early in the build process, I just piled Auralex foam traps into the corner behind the speakers. However, the black foam just doesn't work in the room corners, plus I wanted more absorbtion than these small foam cores provide. The big Auralex foam traps are way too expensive, plus they are black, too. Behind the speakers the usual assortment of diffuser plants as well.